1. Field of the Invention
This invention relates to a positive type resist composition suitable for use as a positive type photoresist sensitive to radiations such as ultraviolet rays including g ray and i ray, far ultraviolet rays including excimer laser and the like, electron beams, ion beams, X ray and the like.
2. Related Art
Compositions comprising a quinonediazide compound and an alkali-soluble resin are used as positive type photoresists, because their quinonediazide groups decompose when irradiated by a light having a wavelength of 500 nm or shorter and, as its result, they change from an alkali-insoluble material to an alkalisoluble material. Since these positive type photoresists are much superior to negative type ones in resolution, they are used for the preparation of integrated circuits such as IC, LSI, etc.
In the current integrated circuits, the improvement in the degree of integration has brought about a decrease in the width of wiring, due to which the hitherto employed wet etching process is being replaced by the dry etching process. Dry etching process is accompanied by an elevation of the substrate temperature, which can result in a deformation of resist pattern and a drop in dimensional accuracy. Thus, at the present time, an improvement of the heat resistance of resist is demanded more earnestly than ever. Further, if a scum remains after the development or the profile is not rectangular, undesirable influences are exercised on the dimension of substrate after dry etching, so that a resist free from scum and giving a good profile is requested. However, if a good pattern profile and a high resolution are aimed at simultaneously, the sensitivity is greatly deteriorated usually. From such a viewpoint, the positive type photoresists today in use cannot be said to be satisfactory in the balance between performances such as sensitivity, profile, scum and heat resistance.